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(#) Suspicious 0dp dimension

!!! ERROR: Suspicious 0dp dimension
   This is an error.

Id
:   `Suspicious0dp`
Summary
:   Suspicious 0dp dimension
Severity
:   Error
Category
:   Correctness
Platform
:   Android
Vendor
:   Android Open Source Project
Feedback
:   https://issuetracker.google.com/issues/new?component=192708
Since
:   Initial
Affects
:   Resource files
Editing
:   This check runs on the fly in the IDE editor
Implementation
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-checks/src/main/java/com/android/tools/lint/checks/InefficientWeightDetector.java)
Tests
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/InefficientWeightDetectorTest.java)
Copyright Year
:   2011

Using 0dp as the width in a horizontal `LinearLayout` with weights is a
useful trick to ensure that only the weights (and not the intrinsic
sizes) are used when sizing the children.

However, if you use 0dp for the opposite dimension, the view will be
invisible. This can happen if you change the orientation of a layout
without also flipping the `0dp` dimension in all the children.

(##) Example

Here is an example of lint warnings produced by this check:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text
res/layout/wrong0dp.xml:19:Error: Suspicious size: this will make the
view invisible, should be used with layout_weight [Suspicious0dp]
    android:layout_width="0dp"
    --------------------------
res/layout/wrong0dp.xml:25:Error: Suspicious size: this will make the
view invisible, should be used with layout_weight [Suspicious0dp]
    android:layout_height="0dp"
    ---------------------------
res/layout/wrong0dp.xml:34:Error: Suspicious size: this will make the
view invisible, probably intended for layout_height [Suspicious0dp]
    android:layout_width="0dp"
    --------------------------
res/layout/wrong0dp.xml:67:Error: Suspicious size: this will make the
view invisible, probably intended for layout_width [Suspicious0dp]
    android:layout_height="0dp"
    ---------------------------
res/layout/wrong0dp.xml:90:Error: Suspicious size: this will make the
view invisible, probably intended for layout_width [Suspicious0dp]
    android:layout_height="0dp"
    ---------------------------
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Here is the source file referenced above:

`res/layout/wrong0dp.xml`:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~xml linenumbers
&lt;?xml version="1.0" encoding="utf-8"?&gt;
&lt;FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:ignore="HardcodedText" &gt;

    &lt;!-- Vertical Layout --&gt;

    &lt;LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical" &gt;

        &lt;!-- No weight: Always an error --&gt;

        &lt;Button
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:text="Button" /&gt;

        &lt;Button
            android:layout_width="wrap_content"
            android:layout_height="0dp"
            android:text="Button" /&gt;

        &lt;!--
             0dp not along the orientation axis is wrong;
             here layout_height is okay, layout_width is not
        --&gt;

        &lt;Button
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1.0"
            android:text="Button" /&gt;

        &lt;!-- OK --&gt;

        &lt;Button
            android:layout_width="wrap_content"
            android:layout_height="0dp"
            android:layout_weight="1.0"
            android:text="Button" /&gt;
    &lt;/LinearLayout&gt;

    &lt;!-- Horizontal Layout --&gt;

    &lt;LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="horizontal" &gt;

        &lt;!-- OK --&gt;

        &lt;Button
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1.0"
            android:text="Button" /&gt;

        &lt;!-- Not OK --&gt;

        &lt;Button
            android:layout_width="wrap_content"
            android:layout_height="0dp"
            android:layout_weight="1.0"
            android:text="Button" /&gt;
    &lt;/LinearLayout&gt;

    &lt;!-- No orientation specified, so horizontal --&gt;

    &lt;LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent" &gt;

        &lt;!-- OK --&gt;

        &lt;Button
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1.0"
            android:text="Button" /&gt;

        &lt;!-- Not OK --&gt;

        &lt;Button
            android:layout_width="wrap_content"
            android:layout_height="0dp"
            android:layout_weight="1.0"
            android:text="Button" /&gt;

        &lt;!-- Check suppressed --&gt;

        &lt;Button
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:text="Button"
            tools:ignore="Suspicious0dp" /&gt;
    &lt;/LinearLayout&gt;

&lt;/FrameLayout&gt;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can also visit the
[source code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/InefficientWeightDetectorTest.java)
for the unit tests for this check to see additional scenarios.

The above example was automatically extracted from the first unit test
found for this lint check, `InefficientWeightDetector.testWrong0Dp`.
To report a problem with this extracted sample, visit
https://issuetracker.google.com/issues/new?component=192708.

(##) Suppressing

You can suppress false positives using one of the following mechanisms:

* Adding the suppression attribute `tools:ignore="Suspicious0dp"` on
  the problematic XML element (or one of its enclosing elements). You
  may also need to add the following namespace declaration on the root
  element in the XML file if it's not already there:
  `xmlns:tools="http://schemas.android.com/tools"`.

  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;LinearLayout xmlns:tools="http://schemas.android.com/tools"
      tools:ignore="Suspicious0dp" ...&gt;
    ...
  &lt;/LinearLayout&gt;
  ```

* Using a special `lint.xml` file in the source tree which turns off
  the check in that folder and any sub folder. A simple file might look
  like this:
  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;lint&gt;
      &lt;issue id="Suspicious0dp" severity="ignore" /&gt;
  &lt;/lint&gt;
  ```
  Instead of `ignore` you can also change the severity here, for
  example from `error` to `warning`. You can find additional
  documentation on how to filter issues by path, regular expression and
  so on
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/lintxml.md.html).

* In Gradle projects, using the DSL syntax to configure lint. For
  example, you can use something like
  ```gradle
  lintOptions {
      disable 'Suspicious0dp'
  }
  ```
  In Android projects this should be nested inside an `android { }`
  block.

* For manual invocations of `lint`, using the `--ignore` flag:
  ```
  $ lint --ignore Suspicious0dp ...`
  ```

* Last, but not least, using baselines, as discussed
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).

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